1. Field
Embodiments described herein relate generally to a semiconductor integrated circuit including a squelch circuit.
2. Background Art
For example, according to serial STA (SATA: Serial Advanced Technology Attachment) which is communication standards between a computer host and a device, either the host or the device transmits a specific pattern (OOB pattern) to the opposite side, when the host and the device return from a power management state with power dissipation reduced or resetting is conducted.
And the receiving side needs to recognize that the sent pattern signal is the OOB pattern signal. A squelch circuit provided in a semiconductor integrated circuit on the receiving side detects the OOB pattern signal by detecting a burst interval and a space interval of the sent pattern signal.
Furthermore, in PCIexpress, the receiving side detects whether the TX side is conducting data transfer (there is a difference signal) or is not conducting the data transfer (there isn't a difference signal).
For testing this squelch circuit, there are high speed testers using a signal of at least several hundred mega bps, low speed testers using a DC (direct current) voltage, and the like.
For example, a test at an actual transfer rate using the high speed tester is expensive, and there is a problem in cost.
In the DC test using the low speed tester, a high precision small amplitude AC (alternating current) signal cannot be input, and consequently it is necessary to use correlation between the DC test and a speed test. If the low speed tester is used, therefore, it is necessary to widen test specifications considering the error of the correlation, resulting in a problem of a lowered yield of the product.
A conventional semiconductor integrated circuit includes a squelch circuit (amplitude determination circuit) and a DC amplitude generation circuit which supplies a differential signal of DC voltages to the squelch circuit at the time of testing for adjusting a threshold.
In this conventional semiconductor integrated circuit, stationary DC voltages are applied to the squelch circuit. In other words, the semiconductor integrated circuit is not a circuit to be tested fast by inputting a high speed data pattern signal. In addition, since a DC amplitude generation circuit is additionally installed, a circuit area of the semiconductor integrated circuit increases.